The primary aims of our research group are to contribute to our understanding of the ecology, evolution, and conservation of tropical vertebrate populations and their habitats, and to apply this understanding to studies of human evolution. Our published work encompasses anthropology, ecology, botany, conservation biology, and animal behavior.

Much of our work is conducted in and around the Cabang Panti Research Station, in Gunung Palung National Park. GPNP is located near the Bornean coast in West Kalimantan, Indonesia. Like other sites on islands and near coasts, the elevational gradient at GPNP is compressed, facilitating data collection in multiple forest types. CPRS contains one of the last remaining undisturbed tracts of lowland tropical rainforest in Borneo and encompasses seven highly distinct tropical forest types ranging in elevation 10 to 1100 m asl, making it well suited to the study of ecological processes across diverse ecological landscapes. The forest types– peat and freshwater swamps and alluvial, lowland sandstone, lowland granite, upland granite and montane forests– differ dramatically in their structure, floristic diversity, soils, plant productivity, and vertebrate densities. In recent years we have also extended sampling along a gradient of human disturbance regimes (including logging and hunting).

Beginning in 2000 and continuously since 2007, we have systematically sampled vertebrate population density, plant phenology, and abiotic conditions across the gradient of natural forests types at Cabang Panti. Since 2015, we have also been monitoring vertebrates using a network of sixty camera traps across the full range of forest types at our site.

Below I highlight some of the topics that my students, collaborators, and I have been working on recently.

Identifying drivers of long-term population dynamics and distribution shifts in tropical vertebrates 

Determining the drivers of long-term population dynamics and distribution shifts of vertebrates is a primary goal of theoretical ecologists and conservation biologists. Despite considerable progress in understanding both topics, key questions remain regarding the relative importance of different regulatory mechanisms and determinants of species distributions, how and why these change over time, and to what extent their effects vary as a function of species traits. In addition, there are substantial gaps in understanding diversity in tropical communities, which are especially threatened by anthropogenic change and may function in distinct ways from their better-studied temperate counterparts. We are using our long-term, intensive monitoring of mammal and bird populations, abiotic conditions, and plant phenology along the broad ecological gradient at GPNP to characterize spatial and temporal population dynamics in a wide range of vertebrate species, assess long-term changes in species-specific distributions, identify abiotic and biotic predictors of these patterns, and test hypotheses about the roles of social system, phylogeny, and functional traits in determining them. 

Mechanisms promoting coexistence in mega-diverse communities

Identifying mechanisms that permit co-existence of species in diverse tropical communities is of great theoretical interest and holds substantial practical relevance for conservation. This information has nevertheless proved elusive, in large part because it is usually unfeasible to gather sufficiently detailed data on all potential competitors across the broad spatial and temporal scales necessary to detect relevant ecological interactions. Our study system provides a unique opportunity to overcome these limitations. We are using our long-term data on diet composition, habitat occupancy, and relative abundances of vertebrate frugivores in 24 families (comprising five mammalian and seven avian Orders) along with our concurrent phenological monitoring to examine the effects of spatial and temporal variation in habitat productivity on patterns of space and resource use. One topic of particular interest is testing hypotheses about the ecological mechanisms that might mitigate the potential for competition in these mega-diverse assemblages, including habitat switching, spatial partitioning, and utilization of distinct foods during periods of fruit scarcity. We aim to identify the ecological mechanisms that currently structure this community, and inform general hypotheses about how mega-diverse communities evolve and persist. 

Population and community ecology of five sympatric cat species

Gunung Palung National Park is one of only two sites on Borneo containing all five native felids. We are currently conducting the first targeted ecological study of an intact cat community in Southeast Asia to answer fundamental scientific questions about felid community and population ecology across complex ecological landscapes, to determine how occupancy is mediated by habitat quality, human disturbance, and interspecific interactions, and to inform conservation strategies that will help preserve intact, functional felid communities in the face of anticipated climatic and land-use changes on Borneo and across Indonesia.

Invasion of Indonesian forests by Bellucia pentamera

Many forests in Western Indonesia, including Gunung Palung National Park in West Kalimantan, are being rapidly colonized by the invasive pioneer Bellucia pentamera (Melastomataceae), a Neotropical tree with a wide native range extending from southern Mexico to the Brazilian Amazon. Work led by my former Ph.D. student Chris Dillis showed that this plant has several traits which make it a highly successful invader, including fruiting at much higher frequency than any native tree species and disproportionately colonizing gaps created by selective logging. We are continuing research to understand the ecological causes and consequences of increased Bellucia presence in our forests, including work on dispersal agents, fruiting phenology, effects on native plant diversity, and implications for vertebrate populations. The system presents an interesting case study from an ecological perspective because plant invasions are relatively uncommon in tropical forests. The conservation aspects are also intriguing, because while Bellucia is likely to lower native plant diversity in our forests, it is also probably raising the carrying capacity of the forests for endangered vertebrate species.

Orangutan conservation science

Orangutans are among the most iconic species in wildlife conservation. Most orangutan populations are severely threatened by habitat loss and illegal killing. Despite many decades of conservation attention, there has been frustratingly little progress and most wild populations will disappear over the next few decades unless threats are abated. Old models are clearly not effectively protecting orangutans, and innovative new concepts are required to ensure long-term persistence of this species. In collaboration with a number of fellow researchers, I have been studying new ways in which orangutan conservation might be more effective in the future. We see potential in new approaches that acknowledge the conservation value of degraded lands, take a broad, landscape-level approach to land-use planning, and address in creative ways the often competing needs of orangutans and economically-disadvantaged people. We are also convinced that success will require work with a wide range of stakeholders, including several entities– such as extractive industries (e.g., mining, forestry) and oil palm companies involved in wholesale land conversion– that conservationists typically view as adversaries.

Conservation biology of other vertebrates

Although the bulk of our conservation science has been in the context of orangutans in Indonesia, we have worked with a range of collaborators on projects that address both theoretical and applied questions relevant to the conservation biology of a range of other vertebrate taxa and in other regions. Recent topics that we have considered include road building in the tropics, correlates of sensitivity to selective logging, apparent competition and extinction risk in endangered ungulate prey, and effects of climate policy on biodiversity conservation.